Compositional effects on the properties of high nitrogen content alkaline-earth silicon oxynitride glasses, AE = Mg, Ca, Sr, Ba

A series of alkaline-earth element containing high nitrogen content oxynitride glasses (AESiON), with AE = Mg, Ca, Sr, Ba, were prepared in order to investigate the compositional effects on the physical properties of the alkaline-earth element. The physical properties were found to change linearly with the concentration of AE elements. The density of the glasses increases substantially with an increase in the AE atomic mass and slightly with an increase in nitrogen ratio. Ba containing glasses shows the value of density 4.16 g/cm³. Glass transition temperatures are found to be higher for Mg glasses, ca. 1020 °C, in comparison with Ba glasses, ca. 895 °C. The hardness of Mg containing glasses shows high values, up to 12.2 GPa and decreases for Ca, Sr and Ba containing glasses. Ba, containing glasses shows high values of refractive index in comparison with the Sr, Ca and Mg containing glasses.     

Effect of doping by transitional elements on properties of chalcogenide glasses

In present work, the results on the influence of doping by transitional elements on thermal, optical, structural and magnetic properties of chalcogenide glasses are presented.Thermal properties (T_g values for undoped and doped glasses) were studied using differential scanning calorimetry technique. Activation energy of glass transition was estimated with the use of Kissinger’s expression. Structural studies were carried with the use of Raman and infrared spectroscopy and X-ray diffraction. Radial electron distribution functions in doped and undoped bulk glasses were obtained and analyzed. In Raman spectra, main observed effect under the introduction of dopants was the change of relative concentration of main and non-stoichiometric structural units characteristic for As₂S₃ glasses. Investigation of influence of transition metals Mn-dopants on the optical properties of As₂S₃ glass was studied in mid-IR region. Pure chalcogenide glasses are diamagnetics. Introduction of transitional and rare earth impurities changes the magnetic properties of investigated chalcogenide glasses.     

Development of phosphate glass-ceramics for bone implants

Porous glass-ceramics were prepared by the controlled crystallization of various phosphate foam glasses. The crystalline phases were detected and the following properties of the materials were studied: — textural properties: porosity, interconnection pore size distribution; — mechanical properties: fracture bending stress, Young's modulus. It is shown that these properties depend not only on the composition of the base glasses, but also upon the grain size of the foaming agent.     

Young׳s modulus,Vickers hardness and indentation fracture toughness of alumino silicate glasses

A wide range of alumino silicate glasses with different network modifier ions (Li, Mg, Na, Ca, Zn, La, Ba, Sr, and Pb) was prepared. The glasses were studied with respect to their mechanical properties: Poisson׳s ratio, Young׳s modulus, Vickers hardness and indentation fracture toughness. These properties were mostly affected by the field strength of network modifier ions. All determined properties increase with increasing field strength of the network modifier ions. The mixed modifier alumino silicate glasses with zinc and magnesium show a positive deviation from linearity with two maxima. Lanthanum containing glasses show larger values of mechanical properties for higher lanthanum concentrations. For magnesium alumino silicate glasses the mechanical properties get smaller with increasing SiO₂ concentration; an effect of the magnesium concentration is not observed. Furthermore, if up to 9 mol% MgO is replaced by MgF₂ the mechanical properties are not significantly affected. Compared to models predicting Young׳s moduli of all studied glass compositions, significant deviations are found.     

Physical and Mechanical Properties of Barium Alkali Silicate Glasses for SOFC Sealing Applications

The physical and mechanical properties of two barium alkali silicate glasses were determined as a function of temperature. Their Young's modulus and Poisson's ratio were determined by resonant ultrasound spectroscopy; their viscosity, thermal expansion, and glass transition temperature were determined using a thermomechanical analyzer. The wetting behavior of the two glasses on alumina and 8 mol% yttria stabilized zirconia (8YSZ) substrates was determined by measuring contact angles in air as a function of temperature and time. Values of Young's modulus for both glasses were in good agreement with those predicted by the Makishima and MacKenzie model. The physical and mechanical properties of these glasses are discussed in the context of their potential use for sealing applications in solid-oxide fuel cells.     

Effects of composition and phase relations on mechanical properties and crystallization of silicate glasses

Crystallization, mechanical properties, and workability are all important for the commercialization and optimization of silicate glass compositions. However, the inter-relations of these properties as a function of glass composition have received little investigation. Soda-lime-silica glasses with Na₂O-MgO-CaO-Al₂O₃-SiO₂ compositions relevant to commercial glass manufacture were experimentally studied and multiple liquidus temperature and viscosity models were used to complement the experimental results. Liquidus temperatures of the fabricated glasses were measured by the temperature gradient technique, and Rietveld refinements were applied to X-Ray powder diffraction (XRD) data for devitrified glasses, enabling quantitative determination of the crystalline and amorphous fractions and the nature of the crystals. Structural properties were investigated by Raman spectroscopy. Acoustic echography, micro-Vicker's indentation, and single-edge-notched bend testing methods were used to measure Young's moduli, hardness, and fracture toughness, respectively. It is shown that it is possible to design lower-melting soda-lime-silica glass compositions without compromising their mechanical and crystallization properties. Unlike Young's modulus, brittleness is highly responsive to the composition in soda-lime-silica glasses, and notably low brittleness values can be obtained in glasses with compositions in the wollastonite primary phase field: an effect that is more pronounced in the silica primary phase field. The measured bulk crystal fractions of the glasses subjected to devitrification at the lowest possible industrial conditioning temperatures indicate that soda-lime-silica glass melts can be conditioned close to their liquidus temperatures within the compositional ranges of the primary phase fields of cristobalite, wollastonite, or their combinations.     

Surface structures of sodium borosilicate glasses from molecular dynamics simulations

Surface plays an important role in the physical and chemical properties of oxide glasses and controls the interactions of these glasses with the environment, thus dominating properties such as the chemical durability and bioactivity. The surface atomic structures of a series of sodium borosilicate glasses were studied using classical molecular dynamics simulations with recently developed compositional dependent partial charge potentials. The surface structural features and defect speciation were characterized and compared with the bulk glasses with the same composition. Our simulation results show that the borosilicate glass surfaces have significantly different chemical compositions and structures as compared to the bulk. The glass surfaces are found to be sodium enriched and behave like borosilicate glasses with higher R (Na₂O/B₂O₃) values. As a result of this composition and associated structure changes, the amount of fourfold boron decreases at the surface and the network connectivity on the surface decreases. In addition to composition variation and local structure environment change, defects such as two‐membered rings and three‐coordinated silicon were also observed on the surface. These unusual surface composition and structure features are expected to significantly impact the chemical and physical properties and the interactions with the environments of sodium borosilicate glasses.     

Photoelastic constants of germanate glasses containing lead and bismuth oxides

Regression equations which accurately approximate the concentration curves of the photoelastic constants of lead bismuth germanate glasses were obtained and the isolines of the photoelastic constants were plotted and graphically illustrate the change in the properties of the glasses in almost the entire glass-formation region of the PbO-Bi₂O₃-GeO₂ system. The partial values of the photoelastic constants of the oxides, components of these glasses, were determined and are in agreement with the values established for glasses of other systems. The data obtained can be used in planning the compositions of effective optical media for fabrication of light and acoustic lines for acousto-optic instruments and glasses with a zero optical stress coefficient.     

Structure–Property Correlations in Y–Ca–Mg–Sialon Glasses: Physical and Mechanical Properties

The physical and mechanical properties of 12 glasses from the Y–(Mg,Ca)–Si–Al–O–N and (Mg,Ca)–Si–Al–O–N systems were investigated. The effect of the substitution of magnesium for calcium through two series of glasses, one consisting of oxides glasses and the other of glasses containing 6 at.% of nitrogen (15 e/o N), was considered. The change of the glass transition temperature through the glass series provides evidence for a mixed-alkaline-earth effect between magnesium and calcium species. The indentation hardness ( H ), Young's modulus ( E ), and indentation fracture toughness ( K _C) were found to increase significantly with either the magnesium or the nitrogen content, and nitrogen also seems to enhance the effect of magnesium on the properties. The network structure was analyzed both by ²⁹Si and ²⁷Al Magic Angle Spinning Nuclear Magnetic Resonance and by neutron scattering experiment, which allows for the estimation of some atomic bond lengths in such complex glasses. Nitrogen was found to have a significant structural effect on the magnesium environment and on the glass polymerization degree, and hence on the glass properties.     

Effect of rare‐earth ion size on elasticity and crack initiation in rare‐earth aluminate glasses

In oxide glasses, “hardness” and “damage‐tolerance” are usually competing attributes. The main reason for this is that hard glasses usually have closely packed structures compared to those of damage‐resistant glasses. Recent progress on the mechanical properties of alumina‐rich glasses has thrown some light on how to obtain hard and damage‐tolerant glasses. In this work, the elastic properties and indentation behavior of a glass system based on (R = La, Sm, Gd, Er, Tm, Y), prepared by an aerodynamic levitation technique, was investigated. It was found that the rare‐earth ions exhibited a strong size effect on the mechanical properties of the glasses. The elastic moduli and hardness increased with the packing density and as the ionic radii of the rare‐earth ions decreased. In addition, the resistance to surface damage by indentation increased with larger rare‐earth cations. Our results show that the elastic properties and damage tolerance of rare‐earth aluminate glasses can be tuned depending on the ionic radii of rare‐earth ions.     

Glasses and sitalls reinforced with polycrystalline fibers

A new trend in modern materials technology was examined: the technology of composite materials based on glasses and sitalls reinforced with different types of ceramic fibers. The basic advantages of these composite materials, the properties of the starting materials (glasses, sitalls, reinforcing fibers), and the properties of the composites based on them were reported. Examples of concrete composite systems and promising areas of their application were cited.     

Structural and microstructural comparison of bioactive melt-derived and gel-derived glasses from CaO-SiO2 binary system

Two glasses from CaO-SiO₂ binary system were obtained by sol-gel and melting techniques. The effect of two different glass obtaining methods was investigated using X-ray diffraction, FTIR, Raman and ²⁹Si MAS NMR spectroscopic methods. The measurements revealed significant differences in the glasses structure. Although both glasses were fully amorphous, the gel-derived glass had a more polymerized structure compared to the melt-derived one. The studied glasses were characterized by BET analysis to provide information about specific surface area of the obtained materials. Apart from microstructural evaluation, thermal properties and in vitro bioactivity study of all glasses were conducted to demonstrate differences in performance of the samples. The formation process of hydroxycarbonate apatite (HCA) layer was investigated using inductively coupled plasma mass spectrometry (ICP-MS) and structural studies.     

Preparation and Properties of Nitrogen-Containing Na2O-B2O3 Glasses

Up to 3.3 wt% nitrogen can be incorporated into Na₂O-B₂O₃ glass melts. The melting procedure is described, and structure models are given. In contrast to N-containing silicate glasses, the borate glasses were transparent; however, micrographs of their fracture surfaces showed some crystallinity. Properties were determined as a function of the N and Na₂O contents of the glasses. Compared with N-containing silicate glasses, the properties of borate glasses are much less changed by the nitrogen introduced.     

Mechanical properties of SPS sintered chalcogenide glass-ceramics with externally doped crystals

The low mechanical properties limit the application of chalcogenide glasses in the infrared lens. This paper proposes a general method for enhancing the mechanical strength of chalcogenide glasses. A series of GaAs crystal-doped Ge₁₀As₂₀Se₁₇Te₅₃ and ZnS crystal-doped As₂S₅ glass-ceramics were prepared by spark plasma sintering (SPS). The effects of crystal doping on the optical and mechanical properties of glass-ceramics were studied utilizing FTIR, XRD, SEM, ultramicroscopy, and Vickers hardness. The results show that adding GaAs crystal and ZnS crystal significantly improves the hardness and fracture toughness of the chalcogenide glasses. The infrared transmittance and mechanical properties can be further improved by reducing the crystal size.     

Dy3+掺杂Ge-Ga-Se硫系玻璃的性质

实验制备了Dy3+掺杂Ge-Ga-Se系统硫系玻璃样品,测试了玻璃的密度、显微硬度、可见-红外透射光谱、荧光光谱以及荧光寿命.根据玻璃的密度计算了玻璃的摩尔体积以及致密度.讨论了玻璃的这些性能随系统平均配位数＜r＞的变化关系.实验结果表明该系统中配位数大于2.67的玻璃在1.3 μm具有较好的发光性能,荧光寿命在440～530μs之间,当玻璃组成位于化学门槛即平均配位数为2.73时玻璃的发光强度最强.     

Coordination State of Boron and Aluminum in Low-Alkali Aluminoborosilicate Glasses

The structure of aluminoborosilicate glasses is considered. It is found that the coordination states of boron and aluminum in glasses may vary depending on the composition, which has a perceptible effect on the properties of glaze glasses. Significant discrepancies were found between the experimental and calculated TCLE values of such glasses, which is due to a changed content of four-coordination boron and the emergence of six-coordination aluminum. Considering these data, it is possible to predict the physicochemical properties of glaze glasses.     

Bioactive Glasses: From Macro to Nano

Bioactive glasses play an important role for the bone defects treatment. Forty years ago, it was discovered the first bioactive glass, Bioglass^®, obtained by melting and used in Orthopedics and Dentistry. Twenty years ago, another family of bioactive glasses obtained by solgel processing was reported. Solgel glasses exhibit high textural properties and quicker bioactive response than melt glasses. However, their presence in the market is scarce which could be explained considering that the improvements they bring do not justify the costs of their translation to product. In the last decade, so-called template glasses exhibiting greater bioactivity than solgel glasses were described. These glasses display high pore volume and ordered mesopore structure, which makes them optimal candidates for hosting biologically active substances. For these characteristics, template glasses are being considered ideal candidates for the scaffolds manufacture used in bone engineering. This article shows the main features of three families of bioactive glasses and the importance of their nanostructure in the bioactivity. We demonstrate here that glasses with identical composition may exhibit very different properties, specifically bioactivity, as a function of their nanostructure. This fact demonstrates the importance of controlling this nanostructure in the design of new bioactive materials for bone regeneration.     

Formation and Properties of GeSe2–Ga2Se3–PbI2 Novel Chalcohalide Glasses

The glass-forming region of the GeSe₂–Ga₂Se₃–PbI₂ system was determined and homogeneous glasses were prepared. The maximum dissolvable PbI₂ can be up to 50 mol%. The structures of glasses were characterized by Raman spectroscopy. The thermal, optical, and some basic physical properties of the glasses were investigated. The results show that GeSe₂–Ga₂Se₃–PbI₂ glasses have a wide region of transmission window (0.7–16 μm) and high refractive index (∼2.5) with the addition of PbI₂. The glasses have good glass-forming ability and high glass transition temperatures. Consequently, these novel glasses may be promising candidate materials for infrared optics and nonlinear optical field.     

Phosphate glasses containing monodisperse Fe3−δO4@SiO2 stellate nanoparticles obtained by melt-quenching process

The challenge to obtain stable glasses containing monodisperse magnetic nanoparticles with controlled size and shape is an exciting and almost unexplored field of research. Such new materials can be used in magneto-photonics or ultra-sensitive magnetic sensors. In this work, for the first time, colorless and transparent bulk glasses containing monodisperse 20 nm Fe_3−δO₄ nanoparticles were prepared by a melt-quenching route. Magnetic nanoparticles were synthesized by thermal decomposition and covered with a stellate mesoporous silica shell in order to protect them against dissolution during the glass melting process. The incorporation of nanoparticles into glasses and the ideal parameters obtained for this system are discussed. The new nanocomposite materials were characterized in order to investigate the structure, thermal, and magnetic properties. Such an original approach is a very promising way to incorporate a wide panel of nanoparticles, including metallic, bimetallic and metal oxide nanoparticles, into a variety of glasses providing new properties to these materials.     

Bioactive glasses and direct effect of increased K2O additive for nuclear shielding performance: A comparative investigation

This study aimed to provide a large-scale investigation on direct effect of K₂O additive nuclear radiation shielding properties of calcium phosphate based bioactive quaternary P₂O₅–CaO–Na₂O–K₂O glasses. A gamma ray attenuation setup has been modeled in MCNPX (v-2.6–0) simulation code using Monte Carlo simulation technique. Next, all the bioactive glasses have been defined considering their chemical properties and material densities, respectively. The mass attenuation coefficients (MAC) have been calculated by using MCNPX code and obtained results have been used for determination of another vital gamma-ray shielding parameters. Moreover, a detailed calculation has been done for determination of exposure buildup factor (EBF) and energy absorption buildup factor (EABF) of investigated bioactive glasses which should be considered as important parameters for interaction properties of ionizing radiation with material environment. In addition, effective removal cross sections for fast neutrons have been calculated. To compare our results, obtained HVL values of the present investigation have been compared with copper oxide and cobalt oxide substituted bioactive glasses. Among the investigated bioactive glasses, the maximum MAC values were reported for PCNK60 sample with higher K₂O additive. It can be concluded that chemical structure of additive materials in the bioactive glasses is strongly related with the radiation attenuation properties of bioactive glasses.